Derrick crown construction



Feb. 18, 1941.' A RAWSQN 2,232,268

DERRI CK CROWN CONSTRUCTION Filed Sept. 12, 1958 s Sheets-Sheet 1 6 INVENTOR.

ATTORNEY.

Feb. 18, 1941. A. RAWSON 2,232.268

DERRICK CROWN CONSTRUCTION 7 Filed Sept. 12, 1958 3 Sheets-Sheet 5 IN VENTOR. 4554/5 4/84 wso/v,

Patented Feb. 18, 1941 PATENT OFFICE DERRICK CROWN CONSTRUCTION Leslie A. Bawson, Los Angeles, Calif.

Application September 12, 1938, Serial No. 229,513 5 Claims. (01. 189-21) My invention relates to the construction of derrick towers and has particular reference to a crown construction, having special utility in connection with derricks used for drilling deep wells, such as oil or gas wells.

In the present construction of oil well derricks it is customary to employ four substantially vertical but inwardly sloping legs or posts which are braced by horizontal and cross bracing members, which support a crown frame at their upper ends. This crown frame is, in the previous types of construction, composed of four members placed to form a rectangle, the ends of the members being secured together by clips which bolt to two adjacent members or by use of equivalent means.

Under heavy loads to which the derrick is subjected, it is found that there is a tendency toward angular displacement of the members forming the crown frame, owing to improper or insufficient bracing of the corners, with the result that one side of the crown frame'becomes off-set relative to the opposite side so as to form a rhombus or rhomboid frame instead of a rectangular frame, this being hazardous in that under such conditions the derrick will collapse when an excessive load is placed thereon.

It is impossible with the present methods of drilling wells of this class to provide diagonal bracing across the rectangular crown portion inasmuch as such bracing would seriously interfere with the operation of the crown equipment. Attempts have been made to solve this problem through the use of caps for attachment to the upper end of each derrick leg, these caps being provided with horizontal upper surfaces to which are attached the beams, comprising the water table. This type of construction tends to improve the rigidity and strength of the crown portion of the derrick, but has the primary and outstanding disadvantage that any torsional loads on the derrick place the bolts, used for securing the water table members, in direct shear. This method of construction in the past has not proven very satisfactory.

It sometimes happens that unanticipated infiuences may require a change in the ground plan of the works appurtenant to the derrick so as to require a revision of the crown structure to conform to the new ground plan. This usually consists in either shifting the crown block along the water table or rotating the water table ninety degrees so as to place the crown blocks axis at right angles to its previous location.

It is therefore a primary object of my invention to overcome the aforementioned disadvantages by providing a unitized crown construction which affords maximum rigidity and strength at the points of greatest stress and at least about one corner described by three adjacent legs of the derrick.

It is an additional object of my invention to provide a crown construction of the character set forth which comprises a prefabricated structural member having great rigidity in a horizontal direction. 10

It is also an object of my invention to provide a novel crown construction of the character set forth in which a plurality of main structural members are inter-tied at a point of minimum stress.

It is also an object of my invention to provide a novel crown construction which permits the ready installation of the water table in either of two positions ninety degrees apart.

It is a further object of my invention to provide a crown construction of the character set forth in which additional bracing is secured through attachment of the water table members adjacent to each of the legs and at points approximately mid-way between the legs.

Other objects and advantages of my invention will be apparent from the study of the following specifications, read in connection with the accompanying drawings, wherein Fig. 1 is a fragmentary perspective view showing the crown construction of my invention;

Fig. 2 is a sectional elevation'taken on line II-II of Fig. 3 transversely of the water table beams and at right angles to Fig. 3 which is a sectional elevation taken on the line IIIIII of Fig. 2;

Fig. 4 is a plan view taken just below the water table as indicated by section line IV--IV of Fig. 2;

Fig. 5 is an elevation illustrating the appearance of my novel crown construction when the water table is removed;

Fig. 6 is a perspective View illustrating a onepiece type of crown construction of 'my invention;

Fig. '7 is an exploded perspective View illustrating a two-piece'type of crown construction employing two U shaped parts;

Fig. 8 is also an exploded perspective view showing a two-piece crown construction, each of the pieces in this construction being L shaped; and 60 Fig. 9 is an exploded perspective view illustrating a type of crown construction of my invention which employs four L shaped parts.

As is well known, the stresses imposed upon the crown portion of the derrick during the drilling operation tend to distort the rectangular shape defined by the crown frame into a rhomboid or diamond shape. The forces. tending to produce this distortion give rise to the greatest stresses at the corners of the rectangular shaped crown frame and minimum stresses at points mid-way between the legs.

It is therefore apparent that a prefabricated crown structure must, in order to overcome the disadvantages hereinbefore set forth, provide great rigidity opposing collapse in a horizontal direction. This may be accomplished, as hereinafter described, by constructing the crown frame in any one of the following manners: (a) prefabricate the frame as a one-piece unit from members having great rigidity in a horizontal direction and with the corners so constructed asto provide great strength to resist collapse of the frame, or (b) assemble the frame from prefabricated members having great rigidity in a horizontal direction in such fashion that connections between members are provided at not more than three corners.

In a rectangular shaped crown frame, for example, three members may be used with a connection at three of the four corners. One corner member must, however, be continuous from one intermediate connection around the corner to the other intermediate connection. The structure is therefore essentially triangular in respect to its inherent rigidity, the triangle being, as is well known in the art, an inherently stable unit of great rigidity.

Inasmuch as any connections which may be located midway between corners of the frame are located at points of low stress, additional joints between members may be there located and connected in a very rigid manner as is described hereinafter. I have hereinafter specified that 40 these connections shall be such as to prevent relative movement between the interconnected members whereby these members act as a rigid structurally continuous member extending between adjacent corners; by which I mean that as 5 employed in the crown frame, these interconnected members function in a structural fashion to transmit between adjacent corners the various loads and forces imposed on these members in exactly the same fashion as if such connection 50 did not exist and a single member extending between adjacent corners were employed.

As a concrete illustration of the application of these principles, I have illustrated in Fig. 1 the upper portion of an oil well derrick which in- 55 cludes upstanding legs 6 inter-connected by a system of girts l and diagonal braces 8. At the extreme upper end of the derrick, a crown frame 9 is installed to rigidly intertie the derrick legs at their termination. A crows nest l0 and a 60 gin-pole I I are provided to facilitate servicing and installing the equipment.

The crown construction or crown frame 9 of my invention may include any of the forms illustrated in Figs. 6 to 9 inclusive, all of which are 65 described in detail hereinafter. The present methods of derrick erection include the use of a hoisting mast rising substantially vertically along the vertical axis of the tower, the mast being used to hoist the various parts into posi- 70 tion preparatory to attachment thereof.

It is readily seen that the single unit type of crown construction 9, illustrated in Fig. 6, would have to be hoisted above the mast, which extends above the top of the derrick, and lowered into 75 place while encircling the mast. This is obviously very difficult of accomplishment. For this reason, and other reasons pertaining to the installation of the types illustrated in Figs. 8 and 9, I have selected the type shown in Fig. '7 as representing the present preferred embodiment of my invention. I recognize, however, the fact that changes in the methods employed in erecting derricks may be such as to cause one or the other of the additional types to become the most desirable.

As best shown in Figs. 4, 5 and 7, the present preferred crown construction 9 of my invention includes two U shaped horizontal plates 12 and I3, which are placed with the upper ends of the Us facing each other so as to form a rectangle. The U shaped plates l2 and I3 are preferably each fabricated from three steel plates l4, l5 and I6, welded as indicated at H and I8 to provide a prefabricated member having great rigidity opposing deformation in a horizontal direction. To the underside of each of the U shaped plates in secured a downwardly projecting U shaped web I 9 which may be fabricated from three plates 20, 2| and 22 welded together as indicated at 23 and 24, and each welded to the horizontal plate directly above so as to form essentially a T section. The downward extending plates 20, 2| and 22 are arranged to slope outwardly to conform to the batter of the derrick leg 6.

t the projecting end of each of the webs 20 and 22 I have provided a series of orifices 25 so that these webs may be attached to the corresponding webs of the opposed U section by means of a connection plate 26 and suitable fastenings such as bolts and nuts 21.

It will be seen that this construction provides a rectangular structure composed of members having essentially a T section with the downwardly extending webs of the T sloping outwardly to conform to the batter of the derrick legs.

While I have illustrated crown members having substantially a T section, it is readily seen that many other sections such as flat plates, angle sections, channel sections, Z sections and others may fulfill the essential requirement of having great rigidity in a horizontal direction. My invention therefore comprehends the use of crown members of any section which will meet this essential requirement.

The unitized structure, previously described, is placed upon the upper ends of the derrick legs 6 with the legs occupying the corners formed by the base and side sections of the U shaped web and is secured thereto as by bolts 28.

In the horizontal or flange portion of the unitized crown structure I provide a series of holes 30 and 3| and a complementary series 30a and 31a, which are employed for the purpose of securing the water table to the crown structure.

The water table, as illustrated in Figs. 2 and 3 normally includes main structural members 32, which are usually'of the I-beam shape, and a pair of auxiliary members 33, disposed at right angles to the main members 32 and attached to the ends thereof by means of connection plates 34 and bolts 35. The auxiliary members 33 are generally formed in a channel section.

I provide suitable bolt holes in the inner flanges of the main members 32 so that when each of said members is placed upon opposite sides of the crown structure in a direction parallel to the sides of the U, they may be there attached by means of bolts passed through the holes 3|. Another series of bolt holes is also provided in the auxiliary members 33 so that these may be attached by means of bolts passed through the aforementioned holes 30. In case it is desired to install the water table at a position rotated degrees from that just described, the securing bolts are passed through the holes 30a and 3Ia.

It will be noted that by providing the holes 3064- and 31a on either side of the connection plate at abutting sides of the U, that attachment of the water table members at this point will provide an additional bracing over the only points of connection in the crown structure and operate to transmit the stresses at that point back to the derrick legs so as to provide a connection of great strength and rigidity.

My unitized crown construction also provides downwardly extending webs 36 at each of the exterior corners of the rectangle, as best shown in Figs. 4 and 5. To these webs are secured, as by bolts 31, the structural members 38 required for supporting the crows nest It.

In Fig. '7 I have illustrated in perspective the form of my invention just described which employs two U shaped members.

Fig. 6 illustrates, in perspective, a simpler form of my invention in which the crown structure 9 is prefabricated as a crown cap comprising a complete rectangle employing horizontal plate-s Ma, i5a, Mia and !5b, which are preferably welded together as indicated at l'l'a, Ill) and I811, I813. To the underside of this flat rectangular frame is secured a downwardly projecting rectangular web 19a which may be fabricated from four plates 20a, Zia, 22a and 21b welded together as indicated at 23a, 23b, and 24a, 24b, and each welded to the horizontal plate directly above so as to form essentially a T section.

The downward extending plates 29a, Zia, 241) and 22a are arranged to slope outwardly to conform to the batter of the derrick leg 6. This form of crown construction may be, of course, provided with suitable holes for attaching the water table members and means for securing the derrick legs in a manner identical with that previously described in connection with the preferred form of my invention.

In Fig. 8 I have illustrated a modified form of two-piece construction which includes two L shaped members I 2a and 13a prefabricated in the same manner as that previously described with respect to the preferred form of my invention, and disposed relative to each other in such fashion as to form a rectangular shape. These members may either be secured to each other as by angle connection plates 26a or by utilizing the upper end of the derrick leg 6 as a connecting angle.

Fig. 9 illustrates a type of construction which employs four L shaped members l2b, I20 and I31), I30. These members are preferably prefabricated in the manner hereinbefore set forth and provided with suitable connection plates 26b and 260 for joining the four members together when they are placed with corresponding arms of the L shapes abutting so as to define a rectangle.

In all of the forms of my invention previously described, the details of fabrication, connection provisions and facilities for attaching the water table beams and the derrick leg are preferably of the same construction as that hereinbefore described in connection with the preferred form of my invention.

It will be noted that each of the types of crown construction of my invention embodies the principles of construction set forth hereinbefore, and that I have therefore provided a method of crown construction for derricks which eliminates thehereinbefore serious weaknesses in derrick construction, and that I have also provided'a crown construction which is particularly adapted to fabrication in the shop prior to installation on the derrick.

It has also been shown that the crown construction of my invention allows the water table to be readily'changed from one position to another disposed at right angles to the first, and that attachment of the water table operates as additional bracing in the crown construction to further increase the strength and rigidity of the structure.

While I have shown and described the preferred embodiment of my invention, I do not desire to be limited to the structure described, except as defined in the appended claims.

I claim:

1. In a crown construction for a derrick including a plurality of upstanding legs, the upper ends of which define a rectangle, a rectangular crown frame secured at its corners to said legs and comprising a plurality of integral crown members, one of said members including at least one corner L-shaped in plan view, said corner extending unbroken about a leg, each of said members including a horizontal flange extending unbroken throughout the length of the member to increase the rigidity of the crown against horizontal forces tending to distort the rectangle in a horizontal plane, and a substantially vertical flange for attachment to the legs; and means interconnecting said members.

2. In a crown construction for a derrick including a plurality of upstanding logs, the upper ends of which define a rectangle, a rectangular crown frame secured at its corners to said legs and comprising a plurality of integral crown members, each member including at least one corner L-shaped in plan View, said member having its L-shaped corner extending unbroken about a leg, each of said members including a horizontal flange extending unbroken throughout the length of the member to increase the rigidity of the crown against horizontal forces tending to distort the rectangle in a horizontal plane, and a substantially vertical flange for attachment to the legs; and means interconnecting said members.

3. In a crown construction for a derrick including four upstanding legs, the upper ends of which define a rectangle, a rectangular crown frame secured at its corners to said legs and comprising a pair of integral crown members each substantially U-shaped in plan view disposed with the sides of one of said members lying in end to end abutting relation with the sides of the other of said members, each of said members extending unbroken about a pair of adjacent legs, each of said members including a horizontal flange extending unbroken throughout the length of the member to increase the rigidity of the crown against horizontal forces tending to distort the rectangle in a horizontal plane, and a substantially vertical flange for attachment to the legs; and means interconnecting said members.

4. In a crown construction for a derrick including four upstanding legs, the upper ends of which define a rectangle, a rectangular crown frame secured at its corners to said legs and comprising a pair of integral crown members each L-shaped inplan view disposed with the internal angle of said L-shape facing inwardly 75 toward the center of saidrectangle and with the arms of each of said members lying in transverse relation with the adjacent arms of the other of said L-shaped members and abutting the ends thereof, each of said members extending unbroken about a leg, each of said members including a horizontal flange extending unbroken throughout the length of the member to increase the rigidity of the crown against horizontal forces tending to distort the rectangle in a horizontal plane, and a substantially vertical flange for attachment to the legs; and means interconnecting said members.

5. In a crown construction for a derrick including four upstanding legs, the upper ends of which define a rectangle, a rectangular crown frame secured at its corners to said legs and comprising four integral crown members each L-shaped in plan view disposed with the internal angle of said L-shape facing inwardly toward the center of said rectangle and with the arm of each of said L-shaped members lying in end to end abutting relation with the corresponding arm of an adjacent L-shaped member, each of said members extending unbroken about a leg, each of said members including a horizontal flange extending unbroken throughout the length of the member to increase the rigidity of the crown against horizontal forces tending to distort the rectangle in a horizontal plane, and a substantially vertical flange for attachment to the legs; and means interconnecting said members.

LESLIE A. RAWSON. 

